All done electronically - it knows where it is - usually
(INS) and the 'earth rate' is applied appropriately. That is 'earth rate. You seem to be trying to cover all sorts of 'spinning gyro' errors (which just do not exist) in your post? Friction - take it as nil. 'Accelerometers' - pretty well perfect. Profile rate - INS driven. Add Schuler Loop tuning and you have a pretty good system. Obviously no software is perfect, but platform errors are pretty well a forgotten item.